Power transistors commonly employed in automotive and industrial electronics require a low on-state resistance (Ron·A), while securing a high voltage blocking capability. For example, a MOS (“metal oxide semiconductor”) power transistor should be capable, depending upon application requirements, to block drain to source voltages Vds of some tens to some hundreds or thousands volts. MOS power transistors typically conduct very large currents which may be up to some hundreds of Amperes at typical gate-source voltage of about 2 to 20V.
Attempts are being made to reduce the on-state resistance. For example, according to concepts, power transistors may be formed in very thin substrates. It is desirable to develop new methods for manufacturing semiconductor devices which may be applied to substrates having very small thicknesses.